This invention relates to a rotor-driven, continuously variable transmission (CVT) machine of the general type described in the specification of European patent No. EP 1592900.
Prior art relevant to CVT machines in general is briefly discussed in the specification of the aforementioned patent.
One category of CVT machines, in widespread use, works on a friction drive principle operating in a traction fluid. A conceptually different type of CVT machine makes use of a cam or rotor-based ratcheting technique. The latter category of machine, which inherently has a higher mechanical efficiency advantage over the friction drive type machine, does however have limitations, of which the applicant is aware, which include one or more of the following:    a) a rippled output i.e. the output rotational speed is not directly and continuously related to the input rotational speed;    b) high stresses which are generated by point contact between a cam and cam followers. This limits the capability to transmit forces;    c) the rotor must be relatively long to achieve a large variation between input and output speeds. This mitigates against use in applications in which small volumes are required;    d) the rotor has a small radius of curvature over a portion of its length. This restricts the size of rotor followers which act on the rotor and this, in turn, reduces the force-transmitting capabilities of the rotor followers;    e) static and dynamic balancing of a rotor, which has a variable cross-section, can be problematic;    f) it can be difficult to obtain adequate spring load, from a biasing element, to keep the cam followers in contact with the cam at a high input rotational speed; and    g) the swivel angles of the rotor followers (i.e. the angular deviations of the rotor followers, from the rotor's longitudinal axis, for a fixed position of the rotor followers relative to the longitudinal axis) tend to be large. This can cause large resultant forces on the rotor followers in the axial direction of the rotor.
Other problems encountered include backlash which can arise in a linkage between a rotor follower and an output shaft—this can cause shock loads, and wear and freewheel drag torque on a one-way clutch which transfers rotational movement from a rocker arm arrangement to an output shaft.
It is an object of the present invention to provide a rotor-based, ratcheting, continuously variable transmission machine which addresses, at least partly, the aforementioned problems.